A Solution for Combined GPS/GLONASS Navigation in Conditions of Limited Satellite Visibility

Changsheng Cai

Abstract:	Combined use of GPS and GLONASS creates additional advantages for navigation user community by improving reliability, availability, and accuracy. Navigation users will significantly benefit from the combined GPS and GLONASS navigation especially in an environment with limited satellite visibility, such as in urban or mountainous areas. But in such situations the visible satellite number is often still insufficient to obtain a position solution even if both GPS and GLONASS measurements are used. This is partly because that at least five visible satellites are required to determine a position due to an offset between the timescales of GPS and GLONASS to be solved. In this paper, a method has been proposed to obtain a position solution with only four visible GPS/GLONASS satellites. The system time offset is determined at the user level when sufficient satellites are available which is then used as a quasi observable when only four satellites are visible or the satellite geometry becomes very poor. In addition to the data from IGS stations, an experiment was also conducted in urban area to assess the proposed method. The results indicate that using the proposed method with only four visible GPS/GLONASS satellites a position solution could be obtained.
Published in:	Proceedings of the 21st International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2008) September 16 - 19, 2008 Savannah International Convention Center Savannah, GA
Pages:	1398 - 1405
Cite this article:	Cai, Changsheng, "A Solution for Combined GPS/GLONASS Navigation in Conditions of Limited Satellite Visibility," Proceedings of the 21st International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2008), Savannah, GA, September 2008, pp. 1398-1405.
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